Presently, most clinically available anti-cancer therapies produce a desired response in only about 10-50% of human cancerous cells tested, and anti-cancer treatments are often accompanied by unwanted side-effects.
Existing methods for measuring the ability of candidate anti-cancer therapies to inhibit or kill cancerous cells include measuring effects on tetrazolium blue reduction in fresh tumor biopsy materials. (Black et al., 1954, J Nat Cancer Inst 14:1147-1158), on cloning of human tumor stem cells, (Salmon et al., 1978, N Engl J Med 298:1321-1327), on the uptake of radiolabeled thymidine by tumor cells in the presence and absence of the anti-cancer agent being tested (Kern et al., 1987, Intl J Cell Cloning 5:421-431), on the differential staining properties of living and dead cells (Weisenthal et al., 1991, Oncology, 5:93-103). The colony formation test is currently favored as a method for determining the effect of a candidate anti-cancer therapy on proliferation of cancerous cells in vitro, although it is understood that tumor cells may not grow well in vitro for a long enough time for the test to be successful. While each of these methods provides some measure of the sensitivity of cancerous cells to a candidate anti-cancer therapy, many of these assays take 1-3 weeks to complete. Generally, neither doctors and patients can wait that long for results.